108 POPULAR ILLUSTRATIONS OF 



its dilatation, which most people have often observed, is due to the 

 alternate action of the horizontal and circular fibres. By examining 

 the diagram the student will observe that both the tentacles and 

 the stomach are prolongations of the body wall, and therefore are 

 similarly organised. At h, Fig. 145 (p. 106), is shown a string of 

 beadlike bodies, which are ova, as seen in the female ; for, although 

 the Actinozoa aie propagated both by budding and fissiperation, 

 there is also a true mode of reproduction by sexes which in the sea- 

 anemones are distinct, although not recognisable by any external 

 character or any mode of examination except that of the bodies seen 

 at h by the microscope. At g, Fig. 145 (p. 106), are shown what 

 represents the convoluted filamentary bodies, which contain thread 

 cells, and which the animal can emit outwardly through minute 

 orifices in the skin, called by Mr. Gosse "cinclides." 



In translucent specimens of the sea-anemone, the six partitions 

 formed by the six lamellae (/, Fig. 146, p. 106) can be clearly seen, 

 and it may also be observed that these lamellae do not go to the bottom 

 of the somatic cavity ; consequently, the spaces formed by these 

 " mesenteries," as they are termed, all communicate most freely with 

 each other. A nervous system has not been yet discovered in the 

 actinea, or sea-anemone ; but as it undoubtedly exists in some of the 

 other Actinozoa, it probably only awaits the discovery of some 

 worker more successful than any has hitherto been. In the margin 

 of the disc of the sea-anemone there are sometimes observed some 

 bright blue specks, which have been thought to be organs of vision, 

 of course in a very rudimentary condition. 



The thoughtful reader will not fail to remark that we have now 

 arrived at a decided step in advance in the organised scale of animal 

 existence, not only in the existence of a free stomach with a 

 sphincter, or muscular structure, by which the opening of the 

 stomach into the somatic cavity (z, Fig. 145, p. 106) is closed and 

 opened according to the necessities of the creature's existence, but 

 also in the differentiation, as it is termed, of the sarcode, of which we 

 have spoken so frequently in our previous chapters, into a system 

 of muscles having both flexor and extensor fibres not as we see in 

 the Calycophoridae, merely in the formation of an apparatus for the 

 special purpose of locomotion, but pervading the whole body, sub- 

 stance, tentacles, and stomach of the animal. 



Now this word differentiation simply means a fact which we 

 cannot explain. Sarcode is the ultimate pabulum, or basis, of all 

 animal structure. It not only exists in the lowly Amoeba, but is the 

 main constituent of all animal bodies. By the vital principle this 

 sarcode is changed, or altered, or differentiated into muscle, bone, 

 brain, nerves, blood vessels, tendons, lungs, heart, and all the alimen- 



